Process for dyeing drawn filaments of aromatic polyamides with basic dye-stuffs in the presence of an organic dye carrier



PROCESS FOR DYEING DRAWN FILAMENTS OF AROMATIC POLYAMIDES WITH BASICDYE- STUFFS IN THE PRESENCE OF AN ORGANIC DYE CARRIER Arturo JorgeRichardson and Robert E. Walck, Jr., Waynesboro, Va., assignors to E. I.du Pont de Nemours and Company, Wilmington, Del., a corporation ofDelaware No Drawing. Filed Dec. 16, 1966, Ser. No. 602,144

Int. Cl. D06p /06 US. Cl. 8-172 2 Clafms ABSTRACT OF DISCLOSURE Aprocess for dyeing a textile formed from an aromatic polyamidecontaining a dye-associable copolymeric unit wherein a drawn filament ofthe said polyamide, e.g., poly(m-phenyleneisophthalamide) andpoly[N,N-m-phenylene bis(meta amino benzamide)isophthalamide], isheat-relaxed prior to dyeing the textile in a dye-bath containing (1) adye to which the copolymeric unit is associable and (2) a dye carrier,e.g., an equal weight mixture of dimethyl terephthalate and benzilide.

BACKGROUND OF THE INVENTION Field of the invention Aromatic polyamideshave been found well-suited for a broad range of utility where exposureto high temperatures is involved. Such polymers and shaped structuresderived therefrom are shown, for example, in the Kwolek et al. US.Patent 3,063,966, which teaches process for their manufacture.Consistent with their excellent utility at high temperature there is astrong tendency for members of this class to crystallize or, by somemechanism not yet defined, to develop a highly consolidated, densestructure. The closely packed molecular configuration of shapedstructures comprising aromatic polyamides known Description of the priorart While the various manipulative steps are individually known in theart, their combination in order to obtain the highly desirable result ofthe present invention is not known to be suggested by the art.

SUMMARY OF THE INVENTION In accordance with the present invention aprocess is provided for dyeing textiles formed from synthetic meta orpara oriented, wholly aromatic polyamides containing from 2 to about 15molar percentage of an aromatic dye associable copolymeric unit whichcomprises heating the drawn filaments of the said textile while the saidfilaments are free to relax to a temperature between about 150 to 280 C.for a period between about l'minute (at the upper temperature) and about45 minutes (at the lower temperature) and thereafter dyeing the saidtextile in a dye-bath containing (1) a dye with which the said 00-polymeric unit is associable and (2) a dye assistant.

3,506,990 Patented Apr. 21, 1970 DEFINITIONS AND STANDARDS By a dyeassistant is meant any organic substance which is substantially inert tothe dyebath under the conditions employed and capable of being absorbedby the shaped aromatic polyamide structure to the indicated extent underthe conditions of dyeing specified. The substance may be a pure compoundor a mixture of compounds.

In the examples K/S refers to the ratio of absorbed light to scatteredlight as measured in the usual manner, using a photometer for measuringincident and reflected light. K/S values are related to apparent depthof dyeing attained; percent dye on fiber is no more complex than impliedfor the expression, being merely an indication of the quantity of dye inor on the fiber which is not removed by a simple scour. Dye yield iscalculated as the ratio of K/S value to the percent dye-on-fiber and isan indication of the effectiveness of the dye taken up by the fiber inproducing visible coloration. Dye yield and percent-exhaust are closelyallied to economy of the dyeing operation and therefore of greatpractical importance. It will be obvious that a very high dye yield isof no commercial importance in a dyeing which gives unacceptably poorpercent-exhaust, since the dye bath normally is discarded following adyeing operation. Likewise, a high percent-exhaust can occur in a dyeingcoincidentally with'a very low dye yield as, for example, in cases wherethe fiber has been delustered by taut annealing at high temperature.Thus, to be acceptable economically a dyeing process must be consideredon the basis of all of the listed criteria and no single criterion maybe used in determining adequacy of a dyeing operation.

The invention is illustrated by the following examples, which are notlimitative. In the examples parts are by weight unless otherwise noted.Inherent viscosity is measured in the usual manner at 25 C., usingdimethyl acetamide, containing 4% lithium chloride, as solvent.

EXAMPLES Example 1 A series of aromatic copolyamides is prepared by aprocess as taught in the Kwolek et al. US. Patent 3,063,-'

966 to comprise as the major constituent metaphenylene isophthalamide(MPD-I) and as copolymeric constituent instances, the tow is exposed forabout one second to rolls.

heated to the indicated temperature while beingrestrained from shrinking(indicated'in Table I as taut). In oth-.

ers, it is heated at 260 C. for 20 or 30 minutes (as indicated in TableI) under no restraint (indicated in TableI as ,relaxed). l

The tows. are then cut to about a 2-inch staple length, and hand-cardedpads are prepared from each lot for dyeing. The pads are dyedindividually under a pressure of 20 p.s.i.g. in 40 times their weight ofa dye-bathof the following parts by weight composition:

C.I. Basic Blue 22 0.l6 Dye assistant (where used) 0.8

Wetting agent 0.1 Acetic acid (to pH 2.9).

Water (to parts total).

Parts 3 4 Yarn identity and treatment history are reported in alsoextracts the residual solvent and salt, and dried for Table I. 5.7seconds over rolls heated to 100 C.

TABLE I v Heating Denier Mole percent Polymer Percent conditions perNaSMPD-I inh. Visc. drawn min. 0.5 filament 1. 57 43s 'Iaut, (320)... 20 1. 57 43s Relaxed, 20 (260).- 2.6 2.5 1.71 438 Tent, 20 (320) 2.1 2.51.62 450 Relaxed, 20 (260).- 2.4 6.0 1.68 450 Tent, 20 (320) 1.3 0.01.68 450 Relaxed, (200 2.2 10.0 1. 43 447 Relaxed, 20 (260).- 2.7

A total of 13 dyeings is made, six without a dye assistant The yarn isknitted on a stoll-knitting machine and the and seven with an equalweight mixture of dimethyl ter- 15 resulting knitted fabric is relaxedat 240 C. for 30 minephthalate and benzanilide as a dye assistant. Thedyeing utes under conditions of no restraint. The relaxed fabric periodsand results obtained are summarized in Table II. is dyed with an aciddye under a pressure of 15 p.s.i.g. The a items each were dyed with thedye assistant, the for two hours, the dye bath having the followingcompob items contained no dye assistant. sition and the ratio of bath totubing being 50/ 1.

TABLE II 2 hours 3 hours Percent Percent Dye Percent Percent Dye K/S onfiber exhaust yield /S on fiber exhaust yield As can be seen from TableII (comparing the various Pt. a and b items) use of the dye assistant iscritical. Further- .CI Index @8215 0.1 more, comparing the 3a versus the4a and the 5a versus Dye Assistant as in Ex. 1 1.0 the 6a sample (eachpair with identical and comparable Wetting agent 0.1 copolymericmodification) substantial improvement of the Sulfuric acid (to pH 1.6).relaxed versus the taut samples can be observed. Water.(to 100 pts.).(Note that although sample Shows a Ielatwely hlgh Dye exhaust is nearlyquantitative. In a comparison dye exhaust it .Shows a P dye yield)Samples with an unmodified MPD-I polymer yarn, it is found that 2a and2b which contained no copolymerlc modlfylng less than 50% of the dye wastaken up by the fiber unit are very poor in dyeing performance.

Without use of superatmospheric pressure, dye pickup Example 3 by thePolymer P thls examPle 18 5 as to This example illustrates suitabilityof the process of pletely unattractive commerclally even Wlth thehighest this invention for dyeing of ordqed copolymers such as level ofmodification by NaSMPD. It will be apparent disclosed i US. 3,232,910.from the tabulateddata that WhBIL HI addition to pres- NN' m phenylenebis meta amino benzamide), abbre sure both a dye asslstant andappreclable modlficatlon by viated MPBB hereinafter, is prepared byreacting two mol- N are efnployedr an attractive increase in dyeabil'parts of meta nitro benzoyl chloride with one mol-part of W ffisultsonly In those Y which 'f f not been heated MPD in DMAc and reduction ofthe resulting dinitro inf taut- U of 1 Part f Sa11Y1amhde for the dyetermediate to the diamine by atmospheric pressure by hyslstant of thisexample provides 100% more dye exhaust drogenation, using Pd 0n carb0nas catalyst a at Yemg- Example 2 To the diamine 154 parts) and 11.4parts of CaSMPD m 1420 parts of DMAc cooled to --20 C. is slowly Thisexample illustrates application of the process of added 101 partsisophthaloyl chloride with good agitathis invention to the acid-dyeingof aromatic polyamide tion. The resulting viscous solution isneutralized by structures. addition of 37 parts dry lime slurried in anadditional To a nitrogen-blanketed solution of 100 parts meta- 100 partsDMAc. After vacuum deaeration with eliminaphenylenediamine (MPD) in 985parts DMAc which has tion of a portion of the DMAc and a small amount ofbeen cooled to 2-0 C. is slowly added 189 parts of a water, the solutionis found to contain a copolymer of .94/.06 molar mixture of isophthaloylchloride/pyridine MPBB-I/CaSMPD-I in a molar ratio of 89/11, suit-2,5-dicarbony1 chloride (I/2,5-Py). The resulting viscous able fordry-spinning to useful fibers. The solution is solution is neutralizedby the addition of 69 parts dry dry spun in a manner equivalent to thatof Example 1 lime slurried in an additional 117 parts of DMAc. The andthe filaments so obtained are extraction-drawn to solution isvacuum-deaerated with elimination of 180 450% of their spun length inhot water. The filaments are parts of DMAc containing a small amount ofwater, after heated at 260 C. for 20-30 minutes under conditions whichit contains'19.5% of a copolymer of MPD-I/MPD- 70 of no restraint.

2,5-Py in a 94/6 molar ratio having an inherent viscosity The filamentsare cut to about 2" (about 5 cm.) staple of 1.58. and hand carded padsmade therefrom. The pads are The solution is dry-spun by means availablein the art dyed at 15 p.s.i.g. for 2 hours at a pH 45, otherwise usingto denier. l8-filament yarn which subsequently is the procedure andformulation of Example 1 The fiber drawn to 316% of its as-spun lengthin hot water, which 7 is found to dye satisfactorily to deep shades.

While the invention has been described with particlar reference tocopolymers of MPD-I, it will be obvious that the process may beadvantageously applied to any aromatic copolyamide (includingterpolymers). The amides which may occur at the major constituent in thearomatic polyamides used in the process of this invention areexemplified by those disclosed in the Kwolek et al., US. Patent3,063,966. Suitable as major con stituents are those based on aromaticdiamines and aromatic diacyl compounds as well as those based onaromatic amino-acyl compounds. The former yield polymers having therepeating structure 0 H H NAr N( JAr-a while the latter yields polymershaving the repeating structure H i Y R -N-Ano N-And' wherein Ar and Arrepresent divalent aromatic residues and may be the same or different.Also useful in the practice of this invention are the variouscombinations, ordered or random, of both types of structures. Orderedcopolymers are illustrated in the Preston US. Patent 3,232,910. Theminor amide constituents are exemplified by those derived from and thelike.

In addition to copolyamides, blends of polyamides where a minorcomponent of the lend is a polyamide containing a dye associablesubstituent may be used in the process of the present invention, theminor component constituting from about 2 to about 15 weight percentageof the blend. A typical blend for such a purpose can be formed by mixing2400 parts of an 18.4% MPD-I polymer solution in DMAc/calcium chloridewith 272 parts of a 20% solution of a CaSMPD-I polymer in DMAc. Thesolution can then be dry spun toafilament.

As pointed out above, the process of this invention is generallyapplicable to aromatic polyamide structures. It is especially useful foraromatic polyamides which strongly tend to consolidate to highly densestructures at high temperature; these are characterized as those havinga well-ordered molecular structure and/ or unsubstituted amidehydrogens. When highly consolidated by heat, structures of polyamidesare not penetrated by dyes available in the trade to a useful extent.The utility of this invention in process for dyeing of such structuresis subject only to three limitations: (1) the polymer must carryfunctional groups which tend to yield stable associations with adyestuff, (2) high temperature exposure in the process for preparationof the shaped structure must be encountered only when the structure isfree to relax, and not exceed 280 C., and (3) a dye assistant isrequired which is, under the conditions of dyeing, absorbed by thestructure to the extent of at least 5%. Typical useful dye assistantsare B-napthol; diphenyl sulfone; salicyl aldehyde; salicylic acid,salicylanilide; dimethyl isophthalate; benzyl alcohol; pelargonic acid;benzoic acid; o-phenyl phenol; dimethyl terephthalate; benzanilide;isopropylidene 4,4'-di-phenol; hexamethyl phosphorarnide; dimethylacetamide; or other members of the homologous series, wherein the acylresidue comprises 1-10 carbon atoms, formic acid and the lowerhomologues thereof, methylene chloride, dimethyl cyanamide,tetramethylene sulfone, 2,4-dimethyltetramethylene sulfone, ethylenediamine, triethylene tetramine, pyrrolidine, pyridine, piperidine,cyclohexylamine, and the like, it being required only that the compoundor mixture employed as a dye assistant must have sufiicient affinity forthe aromatic polyamide structure that it is absorbed by said structureto the indicated extent despite the tendency of many of the materials toform a stable solution in water under the conditions employed. It isrecognized that not all of the materials which are suitable for use as adye-carrier of a shaped structure comprising a given aromatic polymerwill be suitable for use as a dye carrier for structures of all otherpolymers. The requirements are less severe in selection of a carrier fordyeing of a structure comprising a highly modified polymer, and abroader range of carriers is found suitable.

The use of autogenous superatmospheric pressure (5-30 p.s.i.g.) with itsattendant higher temperature is of distinct advantage to this process.In addition, the presence of up to about 15 molar percentage of a secondcopolymeric constituent in addition to the one bearing the dye sensitivesubstituent will tend to break up the well ordered structure of the mainpolyamide chain and further enhance its susceptibility to dyeing. Use ofsuch terpolymers in the copolymeric structure and/or presence of alarger quantity of carrier therein may permit dyeing to a practicaldegree without use of superatmospheric pressure.

In processing the fibers of the present invention it is important thatthey not be exposed to temperatures as high as about 200 C. while tautprior to high-temperature relaxation. Heating of the drawn filamentswhile relaxed for as little as 1 min. at the upper range of tempeaturetreatment is usually adequate for purposes of the present invention.Longer periods are required if lower temperatures are used. Generally adraw of about 4 /2 times extruded length is used to develop good textileproperties in the yarn, and relaxed heating is provided until aneffective draw of about 3 /2 times is reached due to shrinkage in theheat treatment step. The heat relaxation step can be performed upon theyarn, staple or fabric. It is often advantageous to steam the drawn yarn(or staple or fabric) prior to heat relaxation in order to reduceresidual shrinkage in boiling water in the final structure. Suchsteaming does not affect dyeability.

Although only the sodium and calcium salts of the anionic-active minorconstituent of the copolymeric structure have been exemplified, otherneutralizing cations may conveniently and advantageously be employed.Among these are the magnesium, manganese, bismuth, triethyl ammonium,aluminum zinc, ammonium, cadmium, potassium and lithium salts.

The invention is not limited to the exemplified anionicactive orcationic-active copolymeric constituents. It will be apparent to oneskilled in this art that the only criterion of such a constituent isthat it comprise an aromatic-ring substituent of the desiredfunctionality in combination with bifunctional, polyamide-formingcapability. Such a compound may comprise one or more aromatic rings andwhere two or more are involved may comprise additionally alkylene,cycloalkylene or heterocyclic groups therebetween with the limitationthat the chain-extending, amide-precursive groups must, in each case, bedirectly attached to carbon of aromatic rings.

Other bifunctional radicals which may bridge between aromatic moietiesof the starting materials are x0; sulfide, disulfide, methylene,propylene, dimethyl methylene, carbonyl, sulfo, hexafluoroisopropylideneand the like. It is within the scope of this invention to employ anamino carbonyl halide bearing a functional group capable of stableassociation with a dyestuif, as exemplified by 3- amino chlorobenzoyl5-sulfonic acid.

Since many departures from the specifically exemplified embodiments maybe made which are within the spirit and scope of this invention,limitations are to be regarded only as set out in the claims whichfollow.

What is claimed is:

1. A process for dyeing drawn filaments of a copolymer of repeat unitsselected from the group consisting of mphenyleneisophthalamide andN,N'-m-phenylene bis (meta amino benzamide)isophthalamide, and from 2 to15 molar percent of repeat units consisting of the isophthalamide of ametallic salt of 2,4-diaminobenzene sulfonic acid, said processcomprising heating said drawn filaments, while they are free to relax,at a temperature between about 150 to 280 C. for a period of from about1 minute at the upper temperature to about minutes at the lowertemperature and thereafter dyeing said filaments under superatmosphericpressure in an aqueous dyebath containing a basic dye and an organic dyecarrier which is substantially inert to the dyebath under the conditionsemployed and is capable of being absorbed by said filaments to theextent of at least 5% by weight of said filaments under the conditionsemployed.

2. The process of claim 1 wherein said organic dye carrier is an equalweight mixture of dimethyl terephthalate and benzilide.

References Cited UNITED STATES PATENTS 3,184,436 5/1965 Magat 26078GEORGE F. LESMES, Primary Examiner T. I. HERBERT, JR., AssistantExaminer U.S. Cl. X.R.

